Air-conditioner and operation control method thereof

ABSTRACT

An air-conditioner includes a small-capacity compressor and a large-capacity compressor for compressing a refrigerant to a high temperature high pressure gaseous refrigerant; a valve for connecting a suction opening of a refrigerant channel of the large-capacity compressor and a discharge passage of a refrigerant channel of the large-capacity compressor; and a controller for controlling the small-capacity compressor, the large-capacity compressor and the valve.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioner and, moreparticularly, to a method for controlling an operation of theair-conditioner.

2. Description of the Background Art

In general, an air-conditioner includes a compressor for compressing alow temperature low pressure gaseous refrigerant to a high temperaturehigh pressure gaseous refrigerant; a condenser for changing the hightemperature high pressure gaseous refrigerant after being compressed inthe compressor into middle temperature high pressure liquid-staterefrigerant; an electronic expansion Is valve for changing the middletemperature high pressure liquid-state refrigerant to low temperaturelow pressure liquid-state refrigerant; an evaporator for changing thelow temperature low pressure liquid-state refrigerant to a gaseousrefrigerant; and a four-way valve for changing a channel of therefrigerant according to a cooling mode or heating mode.

In the air-conditioner, a role of an indoor heat exchanger and anoutdoor heat exchanger is changed according to the cooling or heatingmode. In the heating mode, the indoor heat exchanger serves as thecondenser and the outdoor heat exchanger serves as the evaporator, andin the cooling mode, the indoor heat exchanger serves as the evaporatorand the outdoor heat exchanger serves as the condenser.

Recently, output capacity of the air-conditioner can be varied accordingto a cooling load or a heating load by using a plurality of compressorseach having different capacity, so cooling and heating efficiency can beoptimized.

FIG. 1 shows the construction of an air-conditioner in accordance with aconventional art.

As shown in FIG. 1, the conventional air-conditioner includes: first andsecond compressors 11 and 12, each having different capacity, forcompressing low temperature low pressure gaseous refrigerant to a hightemperature high pressure gaseous refrigerant; an outdoor heat exchanger14 for heat-exchanging the high temperature high pressure gaseousrefrigerant with outdoor air so as to be condensed to a middletemperature high pressure liquid-state refrigerant; an outdoor fan 14 afor blowing air toward the outdoor heat exchanger; an electronicexpansion valve 15 for changing the middle temperature high pressureliquid-state refrigerant that has passed through the outdoor heatexchanger 14 to a low temperature low pressure liquid-state refrigerant;an indoor heat exchanger 16 for heat-exchanging the low temperature lowpressure liquid-state refrigerant that has passed the electronicexpansion valve with indoor air; an indoor fan 16 a for blowing airtoward the indoor heat exchanger 16; and an accumulator 17 forextracting only the gaseous refrigerant from the refrigerant that haspassed through the indoor heat exchanger 16 and supplying it to thefirst and second compressors 11 and 12.

The air-conditioner also includes check valves 11 a and 12 a forpreventing the refrigerant discharged from a small-capacity compressor11 from flowing back to a large-capacity compressor 12 or therefrigerant discharged from the large compressor 12 from flowing back tothe small-capacity compressor 11; and a four-way valve 13 for settingthe role of the indoor heat exchanger and the outdoor heat exchanger byswitching a channel of the refrigerant that has passed through the firstand second compressors 11 and 12.

In cooling a room, the refrigerant is discharged from two compressors,passes through the check valve and then is condensed in the outdoor heatexchanger. The condensed refrigerant passes through the electronicexpansion valve and is evaporated in the indoor heat exchanger.Thereafter, the evaporated refrigerant passes through a commonaccumulator and then is returned to the compressor. Herein, theoperation of the conventional air-conditioner includes two stages. Thatis, in the first stage, only the first compressor 11 is operated, and inthe second stage, both the first and second compressors 11 and 12 areoperated. Namely, the conventional air-conditioner is operated by twostages.

Herein, after the compressor is stopped from operation, when thecompressor needs to be re-operated, a pressure of the suction openingside and a pressure of the discharge passage should be balanced.However, in the conventional air-conditioner, when the compressor isstopped from operation, the pressure at the discharge passage and thepressure at the suction opening will not be quickly balanced but beslowly equal due to oil and the refrigerant inside the compressor,causing a problem of platen pressure problem, and maximum 30 minutes aretaken until the pressure of the suction opening and the pressure of thedischarge passage are the same.

Thus, in the conventional compressor and the method for controlling theoperation of the compressor, after the small-capacity compressor isoperated, when the large-capacity compressor is actuated, it cannot beimmediately actuated due to the platen pressure problem in the can ofthe large-capacity compressor. That is, the large-capacity compressor isactuated at a point when the pressure of the discharge passage of thelarge-capacity compressor and the pressure of the suction opening becomeequal after the certain time (maximum 30 minutes) elapses. Therefore,the capability of coping with a load of the air-conditionerdeteriorates.

SUMMARY OF THE INVENTION

Therefore, one object of the present invention is to provide anair-conditioner capable of enhancing load coping capability byshortening time to make a pressure of a discharge passage of alarge-capacity compressor and a pressure of a suction opening of thelarge-capacity compressor equal before the large-capacity compressor isstarted for operation while a small-capacity compressor is beingoperated.

Another object of the present invention is to provide a method forcontrolling an operation of the air-conditioner, in which asmall-capacity compressor and a large-capacity compressor are alloperated to perform a cooling operation several times repeatedly, andthen, when an indoor load is increased while only the small-capacitycompressor is operated for cooling a room, a pressure of a dischargepassage of the large-capacity compressor and a pressure of a suctionopening of the small-capacity compressor are made to be equal and thenthe large-capacity compressor is started for perform a coolingoperation, whereby the cooling operation of the air-conditioner isperformed in a high power saving mode.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described herein,there is provided an air-conditioner including: a small-capacitycompressor and a large-capacity compressor for compressing a refrigerantto a high temperature high pressure gaseous refrigerant; a valve forconnecting a suction opening of a refrigerant channel of thelarge-capacity compressor and a discharge passage of a refrigerantchannel of the large-capacity compressor; and a controller forcontrolling the small-capacity compressor, the large-capacity compressorand the valve.

To achieve the above object, there is also provided a method forcontrolling an operation of an air-conditioner including: a first stepin which in case of a cooling operation, a small-capacity compressor anda large-capacity compressor are actuated, and then, when a value of aroom temperature varied by the actuated small-capacity compressor andlarge-capacity compressor is smaller than a value obtained bysubtracting a pre-set first temperature from a desired temperature setby a user, the small-capacity compressor and the large-capacitycompressor are stopped; a second step in which in a state than thesmall-capacity compressor and the large-capacity compressor are stopped,when the value of the room temperature is greater than a value obtainedby adding a pre-set second temperature to the desired temperature, itgoes back to the first step; a third step in which the first and secondsteps are repeatedly performed as many as the pre-set number of times; afourth step in which only the small-capacity compressor is controlled tosatisfy a relation of (desired temperature−pre-set firsttemperature≦room temperature≦(desired temperature−pre-set secondtemperature); a fifth step in which when the value of the roomtemperature is greater than a value obtained by adding a pre-set thirdtemperature to the desired temperature, a valve is operated for acertain time and then stopped; and a sixth step in which thelarge-capacity compressor is actuated.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

In the drawings:

FIG. 1 shows the construction of an air-conditioner in accordance with aconventional art;

FIG. 2 is a graph showing a relation between actuation of asmall-capacity compressor and a large-capacity compressor of theair-conditioner and a pressure in accordance with the conventional art;

FIG. 3 is a block diagram of an air-conditioner in accordance with thepresent invention;

FIGS. 4A and 4B are flow charts of a method for controlling an operationof the air-conditioner in accordance with the present invention; and

FIG. 5 is a graph showing a waveform of a room temperature in the methodfor controlling an operation of the air-conditioner in accordance withthe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An air-conditioner capable of enhancing load coping capability byshortening time to make a pressure of a discharge passage of alarge-capacity compressor and a pressure of a suction opening of thelarge-capacity compressor equal before the large-capacity compressor isstarted for operation while a small-capacity compressor is beingoperated, and a method for controlling an operation of anair-conditioner in which a small-capacity compressor and alarge-capacity compressor are all operated to perform a coolingoperation several times repeatedly, and then, when an indoor load isincreased while only the small-capacity compressor is operated forcooling a room, a pressure of a discharge passage of the large-capacitycompressor and a pressure of a suction opening of the small-capacitycompressor are made to be equal and then the large-capacity compressoris started for perform a cooling operation, whereby the coolingoperation of the air-conditioner is performed in a high power savingmode, in accordance with a preferred embodiment of the present inventionwill now be described with reference to FIGS. 3 to 5.

FIG. 3 is a block diagram of an air-conditioner in accordance with thepresent invention.

As shown in FIG. 3, an air-conditioner in accordance with the presentinvention includes: a small-capacity compressor 31 and a large-capacitycompressor 32 for compressing a refrigerant to a high temperature highpressure gaseous refrigerant; first check value 33 and second checkvalve 34 respectively installed at a discharge passage of a refrigerantchannel of the small-capacity compressor and the large-capacitycompressor; an indoor heat exchanger 35 connected to the first andsecond check valves; an outdoor heat exchanger 36 connected to theindoor heat exchanger; an accumulator 37 connected to the outdoor heatexchanger; a valve for connecting the suction opening and the dischargepassage of the refrigerant channel of a compressor having greatercompression capacity among the small-capacity compressor and thelarge-capacity compressor; and a controller (not shown) for controllingthe valve.

A method for controlling an operation of the air-conditioner inaccordance with the present invention will now be described withreference to FIGS. 4A and 4B.

As shown in FIGS. 4A and 4B, the method for controlling an operation ofthe air-condition includes: a first step in which in case of a coolingoperation, a small-capacity compressor and a large-capacity compressorare actuated, and then, when a value of a room temperature varied by theactuated small-capacity compressor and large-capacity compressor issmaller than a value obtained by subtracting a pre-set first temperaturefrom a desired temperature set by a user, the small-capacity compressorand the large-capacity compressor are stopped; a second step in which ina state than the small-capacity compressor and the large-capacitycompressor are stopped, when the value of the room temperature isgreater than a value obtained by adding a pre-set second temperature tothe desired temperature, it goes back to the first step; a third step inwhich the first and second steps are repeatedly performed as many as thepre-set number of times; a fourth step in which only the small-capacitycompressor is controlled to satisfy a relation of (desiredtemperature−pre-set first temperature≦room which when the value of theroom temperature is greater than a value obtained by adding a pre-setthird temperature to the desired temperature, a valve is operated for acertain time and then stopped; and a sixth step in which thelarge-capacity compressor is actuated.

The operation of the air-conditioner will be described in detail asfollows. The air-conditioner of the present invention is operated by twostages.

First, when a user selects a cooling operation, the small-capacitycompressor 31 compresses the gaseous refrigerant. The compressedrefrigerant flows to the indoor heat exchanger 35 after passing throughthe first check valve 33.

While the small-capacity compressor 31 is being operated, if thelarge-capacity compressor 32 is desired to be operated, the valve 38 isoperated for a certain time before operating the large-capacitycompressor 32. The operation of the large-capacity compressor 32 isperformed when an indoor load is increased. In other words, the roomtemperature is controlled only by the small-capacity compressor 31, andthen, when the room temperature goes gradually up to be higher by apre-set certain temperature than a desired temperature as set by theuser, the large-capacity compressor 32 is then actuated. The reason ofoperating the valve 38 for a certain time is to make the pressure of thesuction opening of the large-capacity compressor 32 into which therefrigerant flows and the pressure of the discharge passage of thelarge-capacity compressor 32 from which the refrigerant is dischargedequal. The certain time during which the valve 38 is operated ispreferably 1 minute and 30 seconds as obtained from experimentation.

If the two compressors of the air-conditioner have the same compressioncapacity, the valve can be installed at either side of the twocompressors.

After passing through the small-capacity compressor 31 and thelarge-capacity compressor 32, the refrigerant flows through the firstand second check valves 33 and 34, and then to the outdoor heatexchanger 36 through the refrigerant channel. The refrigerant is thenintroduced from the outdoor heat exchanger 36 to the accumulator 37 andthen to the small-capacity compressor 31 or to the large-capacitycompressor 32. Through the processes, cooling or heating is performed.

The method for controlling the operation of the air-conditioner will bedescribed in detail with reference to FIG. 5.

FIG. 5 is a graph showing a waveform of a room temperature in the methodfor controlling an operation of the air-conditioner in accordance withthe present invention.

As shown in FIG. 5, when the user selects the cooling operation and theair-conditioner starts its operation, the controller (not shown)actuates both the small-capacity compressor 31 and the large-capacitycompressor 32 in order to lower the room temperature before operation ofthe air-conditioner, namely, in order to resolve the indoor load (stepS401).

The controller compares a value of the room temperature changed by theoperated small-capacity compressor 31 and large-capacity compressor 32and a value obtained by subtracting a pre-set first temperature from adesired temperature set by the user (step S402).

If the value of the room temperature is smaller than the value obtainedby subtracting the pre-set first temperature from the desiredtemperature, the controller stops operation of the small-capacitycompressor 31 and the large-capacity compressor 32 (step S403).

If the value of the room temperature is greater than the value obtainedby subtracting the pre-set first temperature from the desiredtemperature, the controller keeps operating of the small-capacitycompressor 31 and the large-capacity compressor 32. The pre-set firsttemperature is preferably 0.5° C.

After the small-capacity compressor 31 and the large-capacity compressor32 are stopped, the controller compares the increased value of the roomtemperature and a value obtained by adding a pre-set second temperatureto the desired temperature (step S404).

If the increased value of the room temperature is greater than the valueobtained by adding the pre-set second temperature to the desiredtemperature, the controller actuates the small-capacity compressor 31and the large-capacity compressor 32 again (step S401). If the increasedvalue of the room temperature is smaller than the value obtained byadding the pre-set second temperature to the desired temperature, thecontroller maintains the stop state of the smaller-capacity compressor31 and the large-capacitor compressor 32.

By repeatedly performing the steps S401 to S404 for a certain number oftimes, the indoor load can be resolved. Herein, the certain number oftimes is preferably two times.

After repeated performing the steps S401 to S404 for the certain numberof times, if the increased value of the room temperature is greater thana value obtained by adding the pre-set second temperature to the desiredtemperature, the small-capacity compressor is actuated (step S405).Herein, the pre-set second temperature is preferably 0.5° C.

While the small-capacity compressor is being operated, the value of theroom temperature and the value obtained by subtracting the pre-set firsttemperature from the desired temperature (step S406).

If the value of the room temperature is smaller than the value obtainedby subtracting the pre-set first temperature from the desiredtemperature, the small-capacity compressor is stopped (step S407), orotherwise, the small-capacity compressor is continuously operated.

After the small-capacity compressor is stopped, the controller comparesthe value of the room temperature and the value obtained by adding thepre-set second temperature to the desired temperature (step S408).

If the value of the room temperature is smaller than the value obtainedby adding the pre-set second temperature to the desired temperature, thesmall-capacity compressor 31 is maintained in the stop stage.

If the value of the room temperature is greater than the value obtainedby adding the pre-set second temperature to the desired temperature, thecontroller actuates the small-capacity compressor 31 again (step S409).

After the small-capacity compressor 31 is actuated, the value of theroom temperature and a value obtained by adding a pre-set thirdtemperature to the desired temperature are compared (step S410). Herein,the pre-set third temperature is preferably greater than the pre-setfirst and second temperatures.

If the value of the room temperature is greater than the value obtainedby adding the pre-set third temperature to the desired temperature, inorder to make the pressure of the suction opening of the large-capacitycompressor 32 and the pressure of the discharge passage of thelarge-capacity compressor 32 equal, the valve 38 is operated for acertain time and then stopped (step S411).

If the value of the room temperature is smaller than the value obtainedby adding the pre-set third temperature to the desired temperature,operation of the small-capacity compressor 31 is maintained. Herein, thereason why the value of the room temperature is greater than the valueobtained by adding the pre-set third temperature to the desiredtemperature is because it can happens that the room temperature isgradually increased when the room temperature is controlled only by thesmall-capacity compressor 31. The certain time is preferably about 1minute and 30 seconds (the optimum time obtained throughexperimentation).

After the valve 38 is stopped, the large-capacity compressor 32 isactuated to reduce the increased indoor load (step S412).

If the two compressors of the air-conditioner in accordance with thepresent invention have the same capacity, the two compressors can beoperated regardless of an actuation order.

For a heating operation, the air-conditioner is operated according tothe same control method.

As so far described, the air-conditioner and the method for controllingan operation of the air-conditioner of the present invention have thefollowing advantages.

That is, since the time taken for making the pressure of the dischargepassage of the large-capacity compressor and the pressure of the suctionopening of the large-capacity compressor equal before the large-capacitycompressor is actuated while the small-capacity compressor is beingoperated, the load coping capability can be enhanced.

In addition, after the small-capacity compressor and the large-capacitycompressor are all operated to perform a cooling operation and thecooling operation is repeatedly performed for a certain number of times,when an indoor load is increased while only the small-capacitycompressor is operated to perform a cooling operation, the pressure ofthe discharge passage of the large-capacity compressor and the pressureof the suction opening of the small-capacity compressor are made to beequal and then the large-capacity compressor is actuated to perform acooling operation. Accordingly, the cooling operation of theair-conditioner can be performed in the high power saving mode.

As the present invention may be embodied in several forms withoutdeparting from the spirit or essential characteristics thereof, itshould also be understood that the above-described embodiments are notlimited by any of the details of the foregoing description, unlessotherwise specified, but rather should be construed broadly within itsspirit and scope as defined in the appended claims, and therefore allchanges and modifications that fall within the metes and bounds of theclaims, or equivalence of such metes and bounds are therefore intendedto be embraced by the appended claims.

1. An air-conditioner comprising: a small-capacity compressor and alarge-capacity compressor for compressing a refrigerant to a hightemperature high pressure gaseous refrigerant; a valve for connecting asuction opening of a refrigerant channel of the large-capacitycompressor and a discharge passage of a refrigerant channel of thelarge-capacity compressor; and a controller for controlling thesmall-capacity compressor, the large-capacity compressor and the valve.2. The air-conditioner of claim 1, wherein while the small-capacitorcompressor is being operated, the controller operates the valve for acertain time before actuating the large-capacity compressor, and then,the controller operates the large-capacity compressor.
 3. Theair-conditioner of claim 1, wherein the controller performs acontrolling operation by the following steps comprising: a first step inwhich, in case of a cooling operation, a small-capacity compressor and alarge-capacity compressor are actuated, and then, when a value of a roomtemperature varied by the actuated small-capacity compressor andlarge-capacity compressor is smaller than a value obtained bysubtracting a pre-set first temperature from a desired temperature setby a user, the small-capacity compressor and the large-capacitycompressor are stopped; a second step in which in a state than thesmall-capacity compressor and the large-capacity compressor are stopped,when the value of the room temperature is greater than a value obtainedby adding a pre-set second temperature to the desired temperature, itgoes back to the first step; a third step in which the first and secondsteps are repeatedly performed as many as the pre-set number of times; afourth step in which only the small-capacity compressor is controlled tosatisfy a relation of (desired temperature−pre-set firsttemperature≦room temperature≦(desired temperature−pre-set secondtemperature); a fifth step in which when the value of the roomtemperature is greater than a value obtained by adding a pre-set thirdtemperature to the desired temperature, a valve is operated for acertain time and then stopped; and a sixth step in which thelarge-capacity compressor is actuated.
 4. The air-conditioner of claim2, wherein the certain time is 1 minute and 30 seconds.
 5. Theair-conditioner of claim 3, wherein the certain time is 1 minute and 30seconds.
 6. The air-conditioner of claim 3, wherein the pre-set firstand second temperatures are 0.5° C.
 7. The air-conditioner of claim 3,wherein the pre-set third temperature is greater than the pre-set firstand second temperatures.
 8. The air-conditioner of claim 3, wherein thepre-set number of times is two times.
 9. A method for controlling anoperation of an air-conditioner comprising: operating a small-capacitycompressor; making the pressure of a suction end of a refrigerantchannel and a pressure of a discharge end of the refrigerant channel ofa large-capacity compressor equal while the small-capacity compressor isbeing operated; and actuating the large-capacity compressor after makingthe two pressures equal.
 10. A method for controlling an operation of anair-conditioner comprising: a first step in which, in case of a coolingoperation, a small-capacity compressor and a large-capacity compressorare actuated, and then, when a value of a room temperature varied by theactuated small-capacity compressor and large-capacity compressor issmaller than a value obtained by subtracting a pre-set first temperaturefrom a desired temperature set by a user, the small-capacity compressorand the large-capacity compressor are stopped; a second step in which ina state than the small-capacity compressor and the large-capacitycompressor are stopped, when the value of the room temperature isgreater than a value obtained by adding a pre-set second temperature tothe desired temperature, it goes back to the first step; a third step inwhich the first and second steps are repeatedly performed as many as thepre-set number of times; a fourth step in which only the small-capacitycompressor is controlled to satisfy a relation of (desiredtemperature−pre-set first temperature≦room temperature≦(desiredtemperature−pre-set second temperature); a fifth step in which when thevalue of the room temperature is greater than a value obtained by addinga pre-set third temperature to the desired temperature, a valve isoperated for a certain time and then stopped; and a sixth step in whichthe large-capacity compressor is actuated.
 11. The method of claim 10,wherein the fourth step comprises: a step in which after thesmall-capacity compressor is actuated, if the value of the roomtemperature varied by the actuated small-capacity compressor is smallerthan the value obtained by subtracting the pre-set first temperaturefrom the desired temperature, the small-capacity compressor is stopped;and a step in which with the small-capacity compressor stopped, if thevalue of the room temperature is greater than the value obtained byadding the pre-set second temperature to the desired temperature, thesmall-capacity compressor is actuated.
 12. The method of claim 10,wherein the certain time is 1 minute and 30 seconds.
 13. The method ofclaim 10, wherein the pre-set first and second temperatures are 0.5°.14. The method of claim 10, wherein the pre-set third temperature isgreater than the pre-set first and second temperatures.
 15. The methodof claim 10, wherein the pre-set number is two times.
 16. Anair-conditioner comprising: a small-capacity compressor and alarge-capacity compressor for compressing a refrigerant to a hightemperature high pressure gaseous refrigerant; a valve for connecting asuction opening of a refrigerant channel of the large-capacitycompressor and a discharge passage of a refrigerant channel of thelarge-capacity compressor; and a controller for performing a controllingoperation by the following steps comprising: a first step in which, incase of a heating operation, a small-capacity compressor and alarge-capacity compressor are actuated, and then, when a value of a roomtemperature varied by the actuated small-capacity compressor andlarge-capacity compressor is smaller than a value obtained bysubtracting a pre-set first temperature from a desired temperature setby a user, the small-capacity compressor and the large-capacitycompressor are stopped; a second step in which in a state than thesmall-capacity compressor and the large-capacity compressor are stopped,when the value of the room temperature is greater than a value obtainedby adding a pre-set second temperature to the desired temperature, itgoes back to the first step; a third step in which the first and secondsteps are repeatedly performed as many as the pre-set number of times; afourth step in which only the small-capacity compressor is controlled tosatisfy a relation of (desired temperature−pre-set firsttemperature≦room temperature≦(desired temperature−pre-set secondtemperature); a fifth step in which when the value of the roomtemperature is greater than a value obtained by adding a pre-set thirdtemperature to the desired temperature, a valve is operated for acertain time and then stopped; and a sixth step in which thelarge-capacity compressor is actuated.